LCD panels are used in various applications ranging from portable electronic devices to fixed location units, such as video cameras, automobile navigation systems, laptop PCs and industrial machines. The LCD panel itself cannot emit light but must be backlit by a light source. One of the commonly used backlight sources is a cold-cathode fluorescent lamp (CCFL). Usually, a high alternating current (AC) signal is required to ignite and run the CCFL. To generate such a high AC signal from a direct current (DC) power source, e.g., a rechargeable battery, a DC/AC inverter including a power tank and transformers is designed.
In recent years, there has been increasing interest in larger size LCD displays, as required in LCD TV sets and computer monitors, which may require multiple CCFLs to provide necessary illumination. However, conventional circuits for driving multiple CCFLs may suffer from the problem that CCFL currents may not be balanced due to the tolerances of the inverter transformers and the CCFLs. The imbalance of CCFL currents can cause a reduced lifetime of the CCFLs and non-uniformity of the LCD panel brightness.